Taeyeon Kim

Electricity-driven metabolic shift through direct electron uptake by electroactive heterotroph Clostridium pasteurianum

Although microbes directly accepting electrons from a cathode have been applied for CO2 reduction to produce multicarbon-compounds, a high electron demand and low product concentration are critical limitations. Alternatively, the utilization of electrons as a co-reducing power during fermentation has been attempted, but there must be exogenous mediators due to the lack of an electroactive heterotroph. Here, we show that Clostridium pasteurianum DSM 525 simultaneously utilizes both cathode and substrate as electron donors through direct electron transfer. In a cathode compartment poised at +0.045 V vs. SHE, a metabolic shift in C. pasteurianum occurs toward NADH-consuming metabolite production such as butanol from glucose (20% shift in terms of NADH consumption) and 1,3-propandiol from glycerol (21% shift in terms of NADH consumption). Notably, a small amount of electron uptake significantly induces NADH-consuming pathways over the stoichiometric contribution of the electrons as reducing equivalents. Our results demonstrate a previously unknown electroactivity and metabolic shift in the biochemical-producing heterotroph, opening up the possibility of efficient and enhanced production of electron-dense metabolites using electricity.

Enhanced 2,3-Butanediol Production by Optimizing Fermentation Conditions and Engineering Klebsiella oxytoca M1 through Overexpression of Acetoin Reductase

Microbial production of 2,3-butanediol (2,3-BDO) has been attracting increasing interest because of its high value and various industrial applications. In this study, high production of 2,3-BDO using a previously isolated bacterium Klebsiella oxytoca M1 was carried out by optimizing fermentation conditions and overexpressing acetoin reductase (AR). Supplying complex nitrogen sources and using NaOH as a neutralizing agent were found to enhance specific production and yield of 2,3-BDO. In fed-batch fermentations, 2,3-BDO production increased with the agitation speed (109.6 g/L at 300 rpm vs. 118.5 g/L at 400 rpm) along with significantly reduced formation of by-product, but the yield at 400 rpm was lower than that at 300 rpm (0.40 g/g vs. 0.34 g/g) due to acetoin accumulation at 400 rpm. Because AR catalyzing both acetoin reduction and 2,3-BDO oxidation in K. oxytoca M1 revealed more than 8-fold higher reduction activity than oxidation activity, the engineered K. oxytoca M1 overexpressing the budC encoding AR was used in fed-batch fermentation. Finally, acetoin accumulation was significantly reduced by 43% and enhancement of 2,3-BDO concentration (142.5 g/L), yield (0.42 g/g) and productivity (1.47 g/L/h) was achieved compared to performance with the parent strain. This is by far the highest titer of 2,3-BDO achieved by K. oxytoca strains. This notable result could be obtained by finding favorable fermentation conditions for 2,3-BDO production as well as by utilizing the distinct characteristic of AR in K. oxytoca M1 revealing the nature of reductase.

Comparison of Two Commercial Type 1 Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Modified Live Vaccines against Heterologous Type 1 and Type 2 PRRSV Challenge in Growing Pigs

ABSTRACT The objective of the present study was to compare the efficacy of two commercial type 1 porcine reproductive and respiratory syndrome virus (PRRSV) modified live vaccines against heterologous type 1 and type 2 PRRSV challenge in growing pigs. Vaccination with a type 1 PRRSV vaccine reduced the level of viremia after type 1 PRRSV challenge but did not reduce the level of viremia after the type 2 PRRSV challenge in pigs. Increased levels of interleukin-10 (IL-10) stimulated by type 2 PRRSV coincided with the low numbers of type 2 PRRSV-specific interferon gamma-secreting cells (IFN-γ-SC) in vaccinated pigs after type 2 PRRSV challenge, whereas low levels of IL-10 stimulated by type 1 PRRSV coincided with high numbers of type 1 PRRSV-specific IFN-γ-SC in vaccinated pigs after type 1 PRRSV challenge. Additionally, vaccination with the type 1 PRRSV vaccine effectively reduced the lung lesions and type 1 PRRSV nucleic acids in type 1 PRRSV-challenged pigs but did not reduce lung lesions and type 2 PRRSV nucleic acids in type 2 PRRSV-challenged pigs. There were no significant differences between two commercial type 1 PRRSV vaccines against type 1 and type 2 PRRSV challenge based on virological results, immunological responses, and pathological outcomes. This study demonstrates that vaccinating pigs with the type 1 PRRSV vaccine provides partial protection against respiratory disease with heterologous type 1 PRRSV challenge but no protection with heterologous type 2 PRRSV challenge.

Predictors of Undergraduate and Postgraduate Clinical Performance: A Longitudinal Cohort Study

OBJECTIVE Though many medical schools applied various admission criteria in the selection process, the evidence of using those criteria is unclear. This study examined the predictive validity of each admission criterion for student competency. DESIGN, SETTING, AND PARTICIPANTS We conducted a prospective cohort study of all students who matriculated to Seoul National University School of Medicine from 2002 to 2008. Demographic characteristics, admission criteria scores, and clinical competencies based on grade point average (GPA), objective structured clinical examination score, and internship score were obtained for each student to analyze the predictive validity of admission criteria. RESULTS Graduate GPA at the end of 4 years positively correlated with preadmission GPA (p < 0.0001) and written test score (p = 0.012) but negatively correlated with essay test (p = 0.049). Internship score significantly correlated with preadmission GPA and graduate GPA. Regression analysis revealed that the preadmission GPA of the affiliated college and young age at admission could predict GPA, and preadmission GPA and graduate GPA could predict the internship score, which indicates postgraduate clinical performance. CONCLUSIONS These findings suggest that preadmission GPA is a reliable predictor of academic achievement during medical school and postgraduate clinical performance. For assessing nonacademic competencies, further research is needed.

Is remediation program using team-based learning effective for at-risk medical students?

PURPOSE Although remediation and reassessment of at-risk students are essential functions of medical education, there are no guidelines on how best to remediate such students. In this study, we described and examined the effectiveness of a remediation program that was delivered as team-based learning (TBL) sessions. METHODS After a written examination, 15 of 145 fourth-year students were found to require remediation, and assigned to teams of four to five students. Clinical topics related to items of the Korean Medical License Examination were taught in the remediation period of 3 weeks, and all students took reexamination. Changes in test scores were analyzed, and student feedback was documented. RESULTS Students who participated in the remediation program had significantly better total scores on re-examination (remediation group 225.8 to 263.0 vs. control group 290.8 to 304.0, p<0.05). Most students found that the remediation program was instructive and helped them prepare for the examination. Moreover, students gained confidence, and all of them passed the graduation examination. CONCLUSION TBL is an effective method of remediating at-risk students. Further research with regard to the successful design and implementation of a remediation program for at-risk students is needed.

High Production of 2,3-Butanediol (2,3-BD) by Raoultella ornithinolytica B6 via Optimizing Fermentation Conditions and Overexpressing 2,3-BD Synthesis Genes

Biological production of 2,3-butandiol (2,3-BD) has received great attention as an alternative to the petroleum-based 2,3-BD production. In this study, a high production of 2,3-BD in fed-batch fermentation was investigated with a newly isolated bacterium designated as Raoultella ornithinolytica B6. The isolate produced 2,3-BD as the main product using hexoses (glucose, galactose, and fructose), pentose (xylose) and disaccharide (sucrose). The effects of temperature, pH-control schemes, and agitation speeds on 2,3-BD production were explored to optimize the fermentation conditions. Notably, cell growth and 2,3-BD production by R. ornithinolytica B6 were higher at 25°C than at 30°C. When three pH control schemes (no pH control, pH control at 7, and pH control at 5.5 after the pH was decreased to 5.5 during fermentation) were tested, the best 2,3-BD titer and productivity along with reduced by-product formation were achieved with pH control at 5.5. Among different agitation speeds (300, 400, and 500 rpm), the optimum agitation speed was 400 rpm with 2,3-BD titer of 68.27 g/L, but acetic acid was accumulated up to 23.32 g/L. Further enhancement of the 2,3-BD titer (112.19 g/L), yield (0.38 g/g), and productivity (1.35 g/L/h) as well as a significant reduction of acetic acid accumulation (9.71 g/L) was achieved by the overexpression of homologous budABC genes, the 2,3-BD-synthesis genes involved in the conversion of pyruvate to 2,3-BD. This is the first report presenting a high 2,3-BD production by R.ornithinolytica which has attracted little attention with respect to 2,3-BD production, extending the microbial spectrum of 2,3-BD producers.

The Differences in Children's Story Comprehension According to the Types of Reading Media:Paperback Books vs. Electronic Books*

ABSTRACT This study investigated differences in children’s story comprehension as they related to the types of reading media. The participants comprised 62 four-years-olds from two child-care centers located in a middle-income region of Seoul and Gyeonggi Province. In order to control the experience effect, newly developed stories published into two formats of reading media (paperback books and electronic books) were provided to the participants. The results indicated that there were no significant differences in children’s story comprehension depending on the types of reading media. Paperback book readers and electronic book readers did not show any significant difference in story comprehension, which consists of recall, recognition and reasoning tasks. As literature pertaining to children’s usage of electronic books is limited, the present study offers guidelines for the development of children’s reading media and may serve as a useful resource for future studies. Keywords：읽기매체(reading media), 종이책(paperback book), 전자책(electronic book, e-book), 이야기 이해(story comprehension).

What are Computer Games for Adolescents

In this study, we tried to find out various characteristics of adolescents` computer game using out of functionalism. We used in-depth interviews to 18 adolescents to investigate what they think about games and how they use games. Adolescents showed positive perspectives and had mature attitudes to games. Games are leisure activities which can be carried out only after finishing homework, the fiction which is less important than the reality, something that needs proper restriction. Also, peer group strongly affected their game using.

Degradation mechanism of cyanide in water using a UV-LED/H2O2/Cu2+ system

In this study, we developed a UV-LED/H2O2/Cu2+ system to remove cyanide, which is typically present in metal electroplating wastewater. The results showed the synergistic effects of UV-LED, H2O2, and Cu2+ ions on cyanide removal in comparison with UV-LED photolysis, H2O2 oxidation, UV-LED/H2O2, and H2O2/Cu2+ systems. Cyanide was removed completely in 30 min in the UV-LED/H2O2/Cu2+ system, and its loss followed pseudo-first order kinetics. Statistically, both H2O2 and Cu2+ ions showed positive effects on cyanide removal, but Cu2+ ions exhibited a greater effect. The highest cyanide removal rate constant (k = 0.179 min-1) was achieved at pH 11, but the lowest was achieved at pH 12.5 (k = 0.064 min-1) due to the hydrolysis of H2O2 (pKa of H2O2 = 11.75). The presence of dissolved organic matter (DOM) inhibited cyanide removal, and the removal rate constant exhibited a negative linear correlation with DOM (R2 = 0.987). The removal rate of cyanide was enhanced by the addition of Zn2+ ions (from 0.179 to 0.457 min-1), while the co-existence of Ni2+ or Cr+6 ion with Cu2+ ion reduced cyanide removal. The formation of OH radicals in the UV-LED/H2O2/Cu2+ system was verified using an aminophenyl fluorescence (APF) probe. Cyanate ions and ammonia were detected as the byproducts of cyanide decomposition. Finally, an acute toxicity reduction of 64.6% was achieved in the system within 1 h, despite a high initial cyanide concentration (100 mg/L). In terms of removal efficiency and toxicity reduction, the UV-LED/H2O2/Cu2+ system may be an alternative method of cyanide removal from wastewaters.

Design, Fabrication and Analysis of Walking Robot Based on Origami Structure

Recently, there have been many researches about applications of origami to mechanical engineering, which realizes a 3D sturcture by folding a 2D plane material. With this simple manufacturing process, origami was even adopted by some roboticists as a way to build an entirely new robot with benefits in terms of cost, weight, and structural simplicity. In this paper, we propose a new type of a walking robot based on origami structure. Because all the components of the robot that generate gait motion are mechanically connected, it can actually walk forward with only a single actuator. We also showed the similarity of gait trajectories between a kinematic analysis and the actual gait motion measured by video tracking. This result proved the possibility of designing an origami-based robot with the identical gait trajectory as we plan.